The present invention relates to flame retardant compositions. More particularly, the present invention relates to flame retardant nylon plastic compositions and additive compositions which render nylon plastics substantially flame resistant.
Nylon is the generic name for a family of polyamide polymers characterized by the presence of the amide group. The more common types of polyamide or nylon plastics are nylon-6, nylon-6,6, nylon-6,10, nylon-11 and nylon-12.
The nomenclature commonly employed in naming nylons is simply to designate the number of carbons in the repeating units; for example, the polyamide made from caprolactam, which contains six carbons, is known as nylon-6. If aminoundecanoic acid were instead employed, such monomer containing 11 carbon atoms, the resulting polyamide would be designated nylon-11. The reaction between hexamethylenediamine and adipic acid produces nylon-6,6 and, similarly the reaction between sebacic acid and hexamethylenediamine produces nylon-6,10.
The manufacturing process of a particular polyamide is dependent upon the type of polymer being made. Polymerization of lactams, for example, requires opening of the ring structure, followed by linear chain growth. Polymers formed by reaction of amines and acids are produced by polycondensation, with formation of water.
Polyamides that can be processed as solutions can be produced in the form of copolyamides based on combinations of nylon-6,6, nylon-6 and nylon-6,10. These materials have good oil resistance, abrasion resistance and adhesive qualities.
Furthermore, special grades of nylon have been developed for processing as powders. In this case the most success has been achieved with nylon-11, since it possesses a relatively low melting point of 185.degree. C., has low moisture absorption and good chemical resistance.
One shortcoming of all of the foregoing nylon compositions is that they are not very flame resistant under the UL-94 V rating system which, briefly, is as follows:
"UL-94 V-O":
Average flaming and/or glowing after removal of the igniting flame shall not exceed five seconds and none of the specimens shall drip particles which ignite absorbent cotton.
"UL-94 V-I":
Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and none of the specimens shall drip particles which ignite absorbent cotton.
"UL-94 V-II":
Average flaming and/or glowing after removal of the igniting flame shall not exceed 25 seconds and the specimens drip flaming particles which ignite absorbent cotton.
Japanese Kokai, JP 82/76,039, discloses fire resistant polyolefin compounds which contain 1-50% (based on the polyolefin) of the reaction product of a silane or siloxane having two or more halogen or hydroxyl groups with a boron-containing compound, with or without additional silicone oil. Thus, for example, diphenylsilanediol, boric acid and polydimethylsiloxane oil can be reacted to provide a borosiloxane effective for rendering a low density polyethylene substantially flame resistant.
U.S. Pat. No. 4,247,246 to Betts et al. discloses a flame resistant composition comprised of a crosslinked olefin, decabromodiphenyl ether, silicone gum and dibasic lead phthalate.
In U.S. Pat. No. 4,273,691, MacLaury et al., there is disclosed a flame resistant composition comprised of a blend of organic polymer, silicone polymer, and a Group IIA metal carboxylate salt containing six to twenty carbon atoms. Copending patent application Ser. No. 344,167, filed Jan. 29, 1982 (Frye et al.), discloses flame retardant compositions similar to MacLaury et al. but utilize silicone polymers having substantially lower viscosities.
Frye discloses in U.S. Pat. No. 4,387,176, that improved flame retardant or flame resistant thermoplastics are provided by adding thereto a silicone, a silicone resin which is soluble in said silicone and a Group IIA metal organic salt containing 6 or more carbon atoms. Included among the organic polymers which can be used to make the flame resistant compositions of Frye are polyamides such as nylon-6,6 and nylon-12 etc. Although Frye does provide excellent results in that nylon plastic improves from totally consumed by flames in only 175 seconds to a UL-94 rating of V-II, it is nevertheless desirable to provide nylon compositions which have a UL-94 of V-O or V-I.
Each of the foregoing disclosures are incorporated by reference into the instant disclosure.
It should be noted that the terms "flame resistant" and "flame retardant" are used interchangeably throughout and are intended to have the same meaning, i.e. having a UL-94 rating or V-O or V-I.